1. Field
The present invention relates to wireless communication and, more particularly, to a wireless communication system supporting multiple carriers.
2. Discussion of the Background
A wireless communication system generally uses a single bandwidth for data transmission, and respective mobile communication generation use different bandwidths. For example, a 2nd-generation wireless communication system uses a bandwidth of 200 KHz to 1.25 MHz, a 3rd-wireless communication system uses a bandwidth of 5 MHz to 10 MHz. In order to support an increasing transmission capacity, recently, LTE (Long Term Evolution) or IEEE 802.16m continue to extend their bandwidth to 20 MHz or even higher. It may be requisite to increase the bandwidth to enhance transmission capacity, but it is not easy to allocate frequency of a large bandwidth, except for some areas globally.
A carrier aggregation (CA) technique for binding (or grouping) a plurality of physically non-continuous bands in a frequency domain to obtain an effect of using a logically large band has been developed in order to effectively use fragmented small bands. Individual unit carriers bound through carrier aggregation are called component carriers (CCs). Each of the component carriers (CCs) is defined by a single bandwidth and central frequency.
A system for transmitting and/or receiving data in a broadband through a plurality of component carriers is called a CA (Carrier Aggregation) system or a carrier aggregation environment. The CA system supports both a narrowband and a broadband by using one or more carriers. For example, when one carrier corresponds to a bandwidth of 5 MHz, a bandwidth of a maximum of 20 MHz is supported by using four carriers.
In order to operate the CA system, various control signaling is required between a base station (BS) and a user equipment (UE). For example, exchanging of ACK (ACKnowledgement)/NACK (Not-ACKnowledgement) information to perform HARQ (Hybrid Automatic Repeat reQuest), exchanging of CQI (Channel Quality Indicator) indicating downlink channel quality, and the like, are required.
In this connection, however, since a plurality of uplink CCs and a plurality of downlink CCs are used in the multi-CC system, an apparatus and method for exchanging various control signaling between a BS and a UE in such a communication environment are required.